1. Field of the Invention
This invention relates to an electronically controlled valve which senses a leakage of water or other conductive fluid, and shuts off the source of leakage before extensive structural or property damage can occur. By utilizing a microcontroller-based system in conjunction with a novel valve mechanism, this automatic shutoff valve provides a cost-effective system suitable for various household and commercial applications.
2. Description of the Prior Art
There are situations in which no one is present to hear an alarm when a water leak occurs. Broken water lines on water heaters have been responsible for extensive property damage, especially as a result of earthquakes. In the case of automatic dishwashers and clothes washers the breakage of input water hoses or faulty water level sensing switches has also been known to cause extensive property damage.
There are existing devices, such as the "Water Alert.TM." manufactured by Dorlen Products, which provide an audible alarm when the presence of water is detected thus alerting an individual that immediate attention is required. This provides no protection if no one is present at the time the alarm sounds.
Another commercially available system is the "Fluid Guard," manufactured by Fluid Guard Incorporated. This system detects a water leak condition by monitoring the volume of water flow versus time. It has several disadvantages such as a somewhat complex plumbing installation, need for sensitivity and time adjustments, and high cost.
Yet another device is described in U.S. Pat. No. 4,324,268, dated Apr. 13, 1982, and issued to Avram A. Jacobson. Jacobson utilizes a transistor to sense the presence of liquid via a resulting base-to-emitter current. This current causes transistor collector current to flow which is directly drives a latching relay. The relay, when latched on, energizes a solenoid which, in turn, closes the water valve thus shutting off water flow. The system is powered by a rectified AC power source which is isolated from the AC mains by a transformer. While the function of this valve system is apparent, there are several disadvantages. First, if there is a power failure either during or after the valve closure due to a water leak condition, the valve will once again open allowing the water leak to continue. Although Jacobson states that a battery power source can be provided, it is also mentioned that the solenoid coil will produce sufficient heat during extended periods of energization to warrant its location away from the electronic components. With this in mind, it would require a battery of sizable capacity to maintain the valve in a closed condition for long periods of time. Next, while a remote test switch is provided to simulate the presence of a water leak, and thus induce a valve closure, the switch must periodically be manually activated to test the system. This requirement in all likelihood would very seldom, if ever, be performed, thus compromising system reliability. Lastly, the test switch simulates a water leak condition by effectively placing a resistance across the sensing transistor input lines which are physically located within the control circuit enclosure. Such a circuit configuration fails to test for breakage of either or both of the moisture probe connecting wires which would render the system ineffective. Activating the test switch would indicate the system is operating properly in spite of such a failure.